This revised R01 grant addresses the problem of relapse of B-lineage acute lymphoblastic leukemia (B-ALL) after allogeneic hematopoietic stem-cell transplantation (HSCT). We hypothesize that the incidence of cancer relapse following allogeneic HSCT can be reduced by targeting post-transplant B-ALL minimal residual disease (MRD) with adoptively transferred donor-derived T cells genetically modified to be specific for CD19. To consolidate HSCT, we have designed a next-generation chimeric antigen receptor (CAR), designated CD19RCD28, to redirect specificity of T cells to the B-cell lineage-restricted cell-surface molecule CD19 independent of major histocompatibility complex (MHC). Genetically modified CD19RCD28+ T cells activated through chimeric CD28 and CD3-6 lyse B-ALL, upregulate production of IL-2 and anti-apoptotic genes, in a CAR-regulated manner. The Sleeping Beauty (SB) system has been combined with electroporation to introduce the CAR as well as co-express HSV-1 thymidine kinase (TK) for imaging by positron emission tomography (PET). The studies in Aim #1 will now evaluate whether an all-human CD19-specific CAR can be developed (hCD19RCD28) that provides a fully-competent activation signal as determined by CD19-dependent killing, cytokine production, and sustained proliferation in T cells that have been genetically modified by SB transposition. A xenogeneic mouse model of disseminated B-lineage tumor will be used to ascertain the feasibility and safety of adoptive therapy using non-invasive bioluminescent imaging (BLI) and <PET to longitudinally asses the persistence of the infused CAR+TK+ cells and the anti-tumor effect. Aim #2 will evaluate the safety, feasibility and persistence, of infusing escalating doses of donor-derived hCD19RCD28+ T cells with/without TK expression, after allogeneic HSCT for high-risk CD19+ B-ALL. T cells expressing TK will be imaged by PET. If necessary, ganciclovir (GCV) will be given for conditional ablation of TK+ cells in the event of serious toxicity. Correlative studies in Aim #3 will delineate the magnitude and persistence of transferred T cells at the prescribed T-cell Dose Levels using vector-specific Q-PCR and TCR spectratyping analyses on serially acquired specimens. Other correlative studies will evaluate the trafficking to sampled bone marrow (BM) of adoptively transferred T cells and the functional status of transferred T cells in this anatomic site of MRD. Human PET imaging using 2'-Deoxy-20-[18F]fluoro-5-ethyl-1-2-D-arabinofuranosyluracil ([18F]-FEAU) metabolized/trapped by TK co-expressed in infused CAR+ T cells, will be used to evaluate the distribution of adoptively transferred T cells. In aggregate, the results of the studies will facilitate the evolution of targeting post-HSCT MRD with donor-derived CD19-specific T cells for enhanced disease-free survival of patients with B-ALL. LAY SUMMARY: We will infuse CD19-specific T cells after transplantation to improve survival for patients with acute lymphoblastic leukemia.